CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de December 2017, Nr. 6

News from the Test Bench 2Measuring Large Torques with Greater Precision 2

From the Research Department 2Measurement Campaigns on Test Benches Will Accelerate Certification Processes 2

Workshops 38th CWD Workshop 3

Spotlight 3Aachen's Member of the German Parliament, Rudolf Henke, Visits the CWD 3Hanns-Voith Foundation Honours CWD Dissertation 3Patent Procedure for Innovative Plain Bearing Successfully Concluded 3Gear Sturdiness

Dear partners and friends of the CWD,dear readers,

in this edition, we would like to show yousome examples of how we developscientific and technical principles incollaboration with our partners. Theseprinciples are used to integrate systemtest benches, such as those made by theCWD, into the design and certificationprocess for wind turbines even moreeffectively. One vital factor is the improve-ment of torque measurement accuracy atthe hub of the test object. In cooperationwith the Physikalisch-Technische Bundes-anstalt (PTB, national metrology instituteof the Federal Republic of Germany) andothers, we have developed and tested aninnovative sensor that allows torques tobe measured in the Meganewton-metre-range more accurately than ever before.

We see the recognition of the employmentof system test benches in the certificationprocess as a further ground-breakingelement, with which we have evenimpressed the BMWi (Federal Ministry forEconomic Affairs and Energy). We havetaken our first major step in this directionwith the procurement of the jointCertBench project. In cooperation withrenowned partners, we will develop andvalidate standards and processes that willenable the electrical properties of windturbines to be certified on system testbenches and significantly reduce thecomplexity of field campaigns.

I hope you enjoy reading this newsletterand find new points of contact with ourcompany within its pages.

Yours sincerely, Dirk Abel

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� Editorial� In this Issue

� Snap-Shot

The influence of various operating conditions on torque measurements is investigated using the 5-

MNm multicomponent sensor on the CWD system test bench (see page 2).

CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de Page 2

� News from the Test Bench

� From the Research Department

Measuring Large Torques with Greater Precision

Precise measurements of large torques inthe MNm-range are invaluable for deter-mining the efficiency, validating simulationmodels, optimising the control strategy andevaluating the dynamic behaviour of thedrive train in wind turbines (WT). TheCWD's 4-MW system test bench also pro-vides the option of applying torques up to3.4 MNm. Inaccuracies of between two andfive percent had to be accepted with pre-viously available measurement methods.However, the industry's ideal is a fault tole-rance of less than 0.5 percent. Within theframework of the EU-funded project "Tor-que Measurement in MNM range", several

national metrological institutes (PTB, CMI,CEM, VTT) are working with the WT systemtest bench manufacturers CWD, IWES andCENER to develop innovative, traceablecalibration and measurement methods forranges above1 MNm, to reduce measure-ment inaccuracies. In addition, this projectis investigating the effects of multiaxial andparasitic loads on torque measurements.

The newly developed torque calibrationmethod has been in use on the CWDsystem test bench since the end of August.A 5-MNm multicomponent sensor is usedas a transfer standard (see figure). It wascalibrated at PTB for torques of up to 1.1MNm with a standard measurement in-accuracy of 0.15 percent. In Aachen, wealso take into account such system-relatedinfluences as rotation speed, deformation,

temperature distribution in the drive train,axle misalignment and parasitic loadscaused by assembly. Ultimately, the CWD

system test bench is the first in the world tobe calibrated in this way for MNm-rangetorques in line with metrological standards.

Measurement Campaigns on Test Benches Will AccelerateCertification Processes

Which requirements must system testbenches fulfil to be able to determine andcertify the electrical properties of windturbines (WT)? Are the resulting measure-ments different to data collected usingcomparable measurements in the field,and if so, to what extent?

Scientists and engineers employed at theCWD, the Fraunhofer IWES Nordwest,Wobben Research and DevelopmentGmbH, the UL International GmbH (DEWI)metrological institute and FGH Zertifi-zierungsgesellschaft mbH (certificationbody) are pursuing these issues within theframework of the recently launched jointproject CertBench. The transport systemoperators TenneT TSO GmbH, Siemens AGand the Forschungsvereinigung Antriebs-technik e.V. (Research Association for DriveTechnology) are also involved as associatedproject partners. The companies andresearch institutions want to ascertainwhich conditions are required for testingand measurement campaigns conductedon system test benches in line with the FGRtechnical guideline 3 (TR 3) to return resultsthat are as conclusive as field campaigns.

To achieve results that are comparable tothose from field tests, hardware-in-the-loopprocedures are being developed that enablethe actual dynamic behaviour of wind tur-bine rotors and drive trains to be realisticallysimulated on a system test bench. Minimum

requirements for test bench components,load machines and power grid emulatorsare also being derived. In order to validatethe retrieved test bench measurements, awind turbine made by ENERCON (amongstothers) is being measured on the systemtest benches at CWD and WES. The resultsare being compared with data fromcorresponding measurements of anidentical system in the field.

The aim is to employ system test benchesfor reliable measurement of the electricalproperties of WTs. This will considerablyreduce the duration of required measure-ment campaigns. Working as a committee,the partners will use the project results todevelop relevant standards and guidelineseven whilst the project is still in progress inorder to exploit this additional value withinthe framework of the certification process.The project partners hope to significantlyshorten the certification process in themedium term using this approach.

Certification procedure of a wind turbine

Que

lle: P

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CWD NewsCWD – Center for Wind Power Drives der RWTH Aachen | www.cwd.rwth-aachen.de Page 3

� Spotlight

� Workshops

8th CWD Workshop

At the beginning of November, the 8thCWD Workshop took place in Aachen.Three topics formed the main focus: � Nacelle 4.0: Improvement of the profit

model based on wind farm operatingdata

� WT standardisation � Reducing the uncertainty of

aerodynamic load predictions foroptimised design of WT components

Experts from industry and sciences who areinterested in our series of workshops cancontact the organisers at workshop@cwd.rwth-aachen.de.

Aachen's Member of the GermanParliament, Rudolf Henke, Visitsthe CWD

The CDU's member of the German Parlia-ment Rudolf Henke visited the Center forWind Power Drives (CWD) on 7 September,only a few days after winning the constitu-ency seat in the electoral constituency ofthe city of Aachen. This fact-finding missionwas organised and accompanied by mem-bers of the CDU's Vaalserquartier districtassociation. The hosts at CWD took thisopportunity to emphasise the great chal-lenges posed by the development and

operation of very large wind turbines. Natu-rally, current energy policy issues were alsodiscussed in detail.

Hanns-Voith Foundation HonoursCWD Dissertation

The Hanns-Voith Foundation Prize is awar-ded annually for outstanding university dis-sertations in the areas of the engineeringsciences, natural sciences and economicsciences. This year, a jury chaired by Prof.Dr. Dr. e.h. Dr. h.c. mult. Sigmar Wittig (onthe right of the picture) selected six winnersfrom the submitted bachelor and mastertheses for their outstanding work in theareas of hydropower, new materials, drive

technology, paper, economic sciences anddigital solutions. The CWD was amongstthe prize winners in the area of drivetechnology, represented by the masterthesis written by Jonas Gnauert entitled"Konstruktion eines 5 MNm Drehmoment-sensors für Windenergieanlagen- System-prüfstände" (Construction of a 5-MNmTorque Sensor for Wind Turbine SystemTest Benches). The certificate was presen-ted by Meinrad Schad (on the left of thepicture), chairman of the Hanns-VoithFoundation board.

Patent Procedure for Innovative Plain Bearing Successfully Concluded

The WT-GLiTS project is involved with theinvestigation of innovative main rotor plainbearings and, this year, an invention wassubmitted to the patent office. The patentwas granted a few weeks ago. This newbearing design was developed at CWD and

features conical sliding surfaces. Its specialconstruction prevents wear on the edges ofthe bearing. This structure also ensuressimple, self-explanatory and rapid replace-ment of individual bearing segments. This isparticularly the case as, in contrast to earlierroller bearings, there is no longer any needto remove the rotor to replace the parts.

Gear Sturdiness

The project idea "Getrieberobustheit –Methodik zur Ableitung von Testzyklen zurErmittlung der Robustheit von Getrieben fürWindenergieanlagen" (Gear Sturdiness –Method for Deriving Test Cycles to Deter-mine the Sturdiness of Wind Turbine Gears)developed during the CWD Workshop waspositively assessed and approved by theproject sponsors Jülich and BMWi. Theproject begins on 01 October 2017 and hasa volume of around 1.5 million euro. Theproject consortium is formed by the com-panies Vestas, Siemens Winergy, ZF WindPower, Woodward and Schaeffler alongwith the Chair for Wind Power Drives.

� DisclaimerCWD I Center for Wind Power Drives

ACS I Institute for Automation of Complex Power SystemsProf. Dr.-Ing. Antonello Monti

AIA I Institute of AerodynamicsProf. Dr.-Ing. Wolfgang Schröder

CWD I Chair for Wind Power DrivesProf. Dr.-Ing. Georg Jacobs

IEM I Institute of Electrical MachinesProf. Dr.-Ing. habil. Dr. h. c. Kay Hameyer

IRT I Institute of Automatic ControlProf. Dr.-Ing. Dirk Abel

PGS I Institute for Power Generation and Storage Systems Prof. Dr. ir. Dr. h. c. Rik W. De Doncker

WZL I Laboratory for Machine Tools and Production EngineeringProf. Dr.-Ing Christian Brecher

Editorial and Contact:Samuel Leupold, M.Sc.Center for Wind Power DrivesRWTH Aachen University Campus-Boulevard 61 | D-52074 Aachen

Tel.: +49 241 80 90245Fax: +49 241 80 92885E-mail: news@cwd.rwth-aachen.deURL: www.cwd.rwth-aachen.de